Capacitors are passive electrical components that can store energy in an electric field between a pair of electrodes. Capacitors are often used in electronic circuits as energy-storage devices. A wide variety of different types of capacitors have been developed, including small electrolytic capacitors (for example as used in electronic circuits), basic parallel-plate capacitors, and mechanical variable capacitors. In general, for parallel plate capacitors, the capacitance depends on the dielectric constant of the dielectric material of the capacitor, the area of the electrodes, and the distance between the electrodes. Thin-film capacitors are used in electronic circuits and may have various structures, such as metal oxide semiconductor (MOS) type capacitors, PN junction type, polysilicon-insulator-polysilicon (PIP) type, metal-insulator-metal (MIM) type, and other suitable capacitive structures known in the art.
There is a continued desire in the field to produce increasingly complex implantable medical devices that have ever smaller dimensions, such that the capabilities of the device may be enhanced while the profile of the device may be reduced. To this end, a variety of different fabrication techniques have been employed to make implantable medical devices.
Published U.S. Patent application nos. 20060058588; 20050160827; 20050160826; 20050160825; 20050160824; 20050160823; 20040254483; 20040220637; 20040215049 and 20040193021 describe the use of planar processing techniques, such as Micro-Electro-Mechanical Systems (MEMS) fabrication, in the production of medical devices. Deposition techniques that may be employed in certain aspects of fabrication of the structures include, but are not limited to: electroplating, plasma spray, sputtering, e-beam evaporation, physical vapor deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, etc. Material removal techniques include, but are not limited to: reactive ion etching, anisotropic chemical etching, isotropic chemical etching, planarization, e.g., via chemical mechanical polishing, laser ablation, electronic discharge machining (EDM), etc. Also of interest are lithographic protocols.
One known type of material deposition protocol is cathodic arc deposition. In cathodic arc plasma deposition, a form of ion beam deposition, an electrical arc is generated between a cathode and an anode that causes ions from the cathode to be liberated from the cathode and thereby produce an ion beam. The resultant ion beam, i.e., plasma of cathodic material ions, is then contacted with a surface of a substrate (i.e., material on which the structure is to be produced) to deposit a structure on the substrate surface that is made up of the cathodic material, and in certain embodiments element(s) obtained from the atmosphere in which the substrate is present. A number of patents and published applications are available which describe various cathodic arc deposition protocols and systems. Such publications include U.S. Pat. Nos. 6,929,727; 6,821,399; 6,770,178; 6,702,931; 6,663,755; 6,645,354; 6,608,432; 6,602,390; 6,548,817; 6,465,793; 6,465,780; 6,436,254; 6,409,898; 6,331,332; 6,319,369; 6,261,421 ; 6,224,726; 6,036,828; 6,031,239; 6,027,619; 6,026,763; 6,009,829; 5,972,185; 5,932,078; 5,902,462; 5,895,559; 5,518,597; 5,468,363; 5,401,543; 5,317,235; 5,282,944; 5,279,723; 5,269,896; 5,126,030; 4,936,960; and Published U.S. Application Nos.: 20050249983; 20050189218; 20050181238; 20040168637; 20040103845; 20040055538; 20040026242; 20030209424; 20020144893; 20020140334 and 20020139662.
While cathodic arc deposition protocols are known, to the knowledge of the inventors of the present application such protocols have, to date, been used solely in non-medical device applications, such as the production of coatings on large industrial elements, such as rotor blades, etc., as well as in the production of jewelry.
Despite the significant progress that has been made by applying planar processing protocols, such as MEMS protocols, in medical device design and fabrication, there continues to be a need for the development of new fabrication techniques that can be employed to fabricate implantable medical devices that have ever increasing complexity and ever decreasing size specifications. Of particular interest would be the identification of a protocol that could be employed to produce compositions of deposited materials in a desired form, e.g., thick, stress-free layers, porous layers, and layers having crenulations, in a variety of different configurations, including complex three-dimensional configurations.
Yet, prior art techniques applied to form a capacitor on a semiconductor substrate require that the substrate area devoted to the capacitor is not optimally available to support the formation of other electrical elements. There is therefore a long-felt need to provide improved techniques of forming capacitive elements on a semiconductor substrate.